Firecase for LNG doublewall tank

[shvet]

Hello everyone

A question about pressure relief during fire for doublewall vessels and storage tanks e.g. of LNG.
How to calculate heat flux through double wall?

 

[MortenA]

There has to some legislation on this subject in your country. Its almost a philosophical question. A fire so large that it could affect the tank - is there any option but to run like hell?

--- Best regards, Morten Andersen

 

[shvet]

Heat flux model - is it a legislation concern or industry practice? I do not believe this kind of question is philosophical. It is just a personal practice - how do you (your colleagues, a contractor, a mentor) calculate heat flux through doublewall and why?

 

[MortenA]

I would - as an exercise - do it by the book (api 521) and then i would see if i could come up with an F factor and remember to check for the height. You will need an U value.

Thats because i would think of this case as a relevant case...

Best regards,

--- Best regards, Morten Andersen

 

[georgeverghese]

View factor for radiation between outer wall and inner wall F21 is nearly 1.0 from graph in the section on Radiation in the chapter on Heat Transfer in Perry. There is specific discussion on heat transport in cryogenic storage vessels in the section on cryogenic processes in the chapter on heat transfer equipment design( where you can see view factor for radiative component is 1.0). Is the double wall in your case filled with perlite or near vacuum ? k values for the conductive component for various fill materials are also disclosed in table 11-26 in the 7th edn of Perry.

 

[don1980]

Refer to a text that explains heat transfer through a composite wall. With a double wall you have multiple layers of thermal resistance. Do that to calculate the heat transfer rate to the fluid in contact with the inner wall.

The heat input rate to the LPG will obviously be much less than that of a typical (single wall) API tank.